There’s a lot of excitement about the star known as TRAPPIST-1, which appears to have a set of 7 planets, as determined from measurements of reductions of the star's during transits of the planets. “Is this proof we’re not alone?” newspapers are asking excitedly as three of the planets lie within a “habitable zone”, in which the surface temperature could be right for living organisms to survive.
But before we get too excited, let’s consider a few facts. The Earth orbits its star at a distance of 93 million miles. Planet 4 of this first discovery of the Belgian operated Transiting Planets and Planetesimals Small Telescope-South in Chile lies some 3.5 million miles from its star. It whizzes round that star in a ‘year’ lasting between 2 and 4 weeks, and it is so close to the star that one side is likely to remain facing the star at all times.
As a result, this most likely candidate for life as we know it will have one side in permanent day, the other side in permanent frozen night, and any atmosphere will be blasting constantly at gale force around the planet, and also blasted off the planet by flares and radiation from the star. Even worse, the planet will be bombarded by enough X-rays and extreme UV to have a significant effect on the atmosphere and anything on the surface.
So maybe we shouldn’t get too excited just yet.
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